Single component neutrally buoyant proppant

Abstract

Proppant used to keep open a fissure in a reservoir created by hydraulic or other action is disclosed. The proppant demonstrates a reduced specific gravity controlled by the geometry of the structure of the proppant. Proppant must be capable of withstanding the hydrostatic environment of the hydraulic pumping system, pass through a perforation in the casing of the well, travel into the fissure, and, upon reduction of hydrostatic pressure, withstand the closure pressure of the formation. A proppant having neutral buoyancy or substantial neutral buoyancy yet capable of withstanding the hydraulic and closure pressures is described that has a tubular structure hollow in the center with a wall of material sufficiently strong to withstand the majority of closure pressures.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 61 / 420,941, filed Dec. 8, 2010, the contents of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates generally to proppants for use in hydraulic fracturing and more particularly to neutrally buoyant proppants.BACKGROUND OF INVENTION[0003]The need for energy has spawned numerous new techniques for recovering hydrocarbons from more and more challenging reservoir environments. One such effort has been the recovery of gas from tight rock formation. In these formations, the rock has a low porosity but the entrapped gas is at high pressures within the rock. Wells are drilled into this rock to liberate the gas and collect it in the well itself for recovery and distribution. Such wells are cased with a steel liner which is cemented to the formation. To generate a communication channel to the rock containing the gas, perforation ...

AI Technical Summary

Problems solved by technology

This provides very limited penetration into the gas bearing rock and, therefore, limited ability for the gas to move to the well bore.

This means the rock experiences an relatively low surface pressure while experiencing extremely high internal pressures.

Failure of the proppant can occur if the formation pressure is so great that the stress on the particle exceeds its strength and the proppant particles break.

In addition, structural failure can produce fragments of the proppant which further fill the void space and reduce overall conductivity.

Additionally, the thickening agents themselves have deleterious effects.

The agents and fracturing fluids flow back up the well bore causing a disposal problem.

Additionally, some fraction of these agents typically remains trapped in the proppant bed, reducing its permeability.

However, these lighter materials tend to introduce other limitations.

While walnut shells would penetrate deeper into the formation, their structural strength limits their applicability to relatively small formation closure pressures.

However, the material may remain porous and allow degradation during exposure to the fracturing fluid or well flow.

This does improve their strength but with limitations and at the cost of some of the buoyancy.

However, the material strength of the sand remains limited and, if exceeded, fractures producing small fragments which can occlude the interstitial spacing comprising the percolation network.

Some coatings may be applied to capture these fragments but then are not designed for reduced or neutral buoyancy.

While the coating may reduce the flow of small fragments, the overall change of the size of the fragments of a particle once broken by entropy will occupy more space than they did before breakage.

In addition, the coating will occupy space.

Therefore, even coated proppant meant to capture these “fines” will have reduced conductivity if the particle fails.

However, the materials necessary to produce these hard materials provide strength but at a significant cost in specific gravity.

While the hardness reduces the structural shortcomings, it exacerbates the difficulty of placement into the fractures.

However, this same pressure forces some of the fracturing fluid into the pores of the formation rock.

It is believed that this further reduces the recovery of gas or oil from the reservoir.

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